Search Text in stored procedure in SQL Server

SELECT DISTINCT
o.name AS Object_Name,
o.type_desc
FROM sys.sql_modules m
INNER JOIN
sys.objects o
ON m.object_id = o.object_id
WHERE m.definition Like '%[ABD]%' ESCAPE '\'

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Escape the square brackets:
...
WHERE m.definition Like '%[ABD]%' ESCAPE '\'

Then the square brackets will be treated as a string literals not as wild cards.